1. Field of the Invention
The present invention relates to an organic EL display device.
2. Description of the Related Art
In recent years, organic EL display devices have been increasingly developed. Moreover, an organic EL display device for representing a multiple tone to each pixel of the organic EL display device, and an organic EL display device for realizing a full-color display are becoming popular.
JP2005-148306A discloses, in order to represent multiple tone for each pixel displayed by the organic EL display device, controlling the magnitude of current flowing through the light-emitting elements included in each pixel with the use of a current programming system, and displaying the tone in a pixel circuit using an area coverage tone method if the tone is equal to or lower than a given tone level, and displaying the tone in a pixel circuit using a current programming system if the tone is higher than the given tone level.
JP2004-226673A discloses, in order to prevent a change in color balance due to changes in current density, expressing the tone with use of a pulse width modulation control or an area coverage tone control.
When a current flowing in a light emitting element is reduced for the purpose of expressing a low tone (brightness), a density of the current flowing in the light emitting element is reduced. In the organic EL (electro-luminescence) light emitting element, if the current density drops below a certain level, the brightness control becomes difficult.